Refractory Bricks

Boiler refractory bricks

Aug 02,2022

When the circulating fluidized bed boiler is put into operation, the serious wear of the boiler refractory bricks and boiler refractory castables affects the long-term service life of the boiler. For this reason, many thermal power plants and production units have carried out a lot of research work. The wear resistance of lined refractory bricks and refractory castables has been greatly improved. 

The wear condition of the boiler body is roughly divided into a high temperature wear area and a low temperature light wear area. For the high temperature cyclone separator type boiler, the two parts take the cyclone separator outlet as the dividing line. Before the outlet of the cyclone separator is the high temperature and easy to wear area, which mainly includes the fluidized bed, the return bed, the guard belt, the inertia chamber, the short flue at the furnace outlet, the cyclone separator and the return pipe. After the cyclone separator is the low temperature wear area, which mainly includes refractory materials in the high and low temperature superheater area and the economizer area. Compared with the high temperature easy-wear zone and the low temperature light grinding zone, the working temperature of the former is 850~1050℃, and the latter is 400~800℃. The former is the material circulation area of the boiler, and the latter is the heat exchange flow area at the rear of the boiler. The flow concentration of the former is much larger than that of the latter, and the particle size of the material in the former area is also much larger than that of the latter, so it also determines the difference in the use of refractory materials in the high temperature wear area and the low temperature light grinding area. 

The use models of boiler refractory bricks are divided into ordinary type refractory bricks and customized special-shaped refractory bricks. The materials are ordinary clay refractory bricks and high-alumina refractory bricks. They are made of high-alumina bauxite and sintered at high temperature. They are cheap and widely used in industry. Chain boilers and pulverized coal furnaces, but their anti-wear performance is poor, in circulating fluidized bed boilers, they can generally only be used in low-temperature light grinding areas to build furnace walls. 

Boiler refractory bricks also have a common material that is widely used. Phosphate refractory bricks are made of sintered high alumina bauxite as aggregate, high alumina fine powder as matrix, industrial sulfuric acid as binder, and are pressed and formed by a press. 

Although there are better materials in boiler refractory bricks, such as corundum bricks, silicon carbide bricks, etc., silicon carbide bricks have high wear resistance and good thermal shock when used in high temperature and oxygen-free atmosphere. Stability, after sintering at a certain temperature, a glaze protective layer is formed on the surface. However, according to the use of circulating fluidized bed boilers, silicon carbide refractory bricks cannot achieve satisfactory results for circulating fluidized bed boilers, mainly because the circulating fluidized bed boilers have a small amount of oxygen atmosphere in the combustion. The use of such refractory bricks in oxygen-rich areas is easy to be delaminated by oxidation and lose wear resistance.

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